1. Field of Art
The present invention relates to a portable device maintenance support apparatus, system, and method. More specifically, the present invention relates to a portable apparatus, system, and method preferable for maintenance work such as inspection and adjustment of field devices at the installation location thereof.
The present application claims priority based on Japanese Patent Application No. 2012-183090, filed on Aug. 22, 2012, which is included herein by reference.
2. Background Art
FIG. 8 is a system configuration diagram of an example of a conventional instrumentation system 50. Specifically, FIG. 8 is a system configuration drawing showing an example of an instrumentation system in a control plant such as a petroleum, chemical, steel, paper pulp, gas, LNG, electrical power, water environment, pharmaceuticals.
In FIG. 8, field devices 1 such as temperature transmitters, flow gauges, pressure transmitters, or valve positioners are connected to an upstream control system 3 (also referred to as an upstream system) via an I/O module 2.
The field devices 1 that detect various physical quantities transmit process values. For example, a field device 1 performs hybrid communication by a compound signal, in which a digital signal that includes device information is superimposed onto a 4 to 20 mA analog signal.
In this case, a field device 1 and the control system 3 that perform hybrid communication are basically connected in a one-to-one relationship. The control system 3, based on process values and device information transmitted and input from the field device 1, controls an actuator of a valve or the like.
In the case in which a parameter of a field device 1 is accessed from the control system 3, or in which device information or the like is transmitted from a field device 1 to the control system 3, the digital signal superimposed onto the 4 to 20 mA analog signal is used to perform the desired data receiving and transmitting, in accordance with a prescribed hybrid communication transmission scheme.
Hybrid communication protocols include Foundation® Fieldbus, Profibus®, HART®, MODBUS®, and the like, data receiving and transmitting being performed in accordance with each communication rule.
At the installation location of the field devices 1 constituting the instrumentation system 50 shown in FIG. 8, the hand-held communication and diagnostic device 22 (FIG. 9) as described, for example, in the Published Japanese Translation of the PCT Application 2005-522069 has been proposed as an apparatus for use in maintenance work such as inspection and adjustment of the field devices 1.
In FIG. 9, the hand-held communication and diagnostic device 22 has three network connection terminals 24a, 24b, and 24c. Specifically, the hand-held communication and diagnostic device 22 has two positive terminals (24a and 24c) and one common terminal (24b). The positive terminal 24a and the common terminal 24b are used to connect the hand-held communication and diagnostic device 22 to a HART network. The positive terminal 24c and the common terminal 24b are used to connect the hand-held communication and diagnostic device 22 to a Foundation Fieldbus (sometimes abbreviated FF hereinafter) network.
FIG. 9 shows, as one example, the case in which one of the terminals of a field device 1 is connected to the positive terminal 24a, and another terminal thereof is connected to the common terminal 24b. 
When the hand-held communication and diagnostic device 22 is operating connected in a HART process control loop, it is necessary to prevent sinking or sourcing of a direct current. Given this, a HART physical layer circuit (HARTMAU) 26 is designed so as to supply a voltage signal to the process control loop (not shown).
In order to satisfy intrinsic safety requirements in the FF, the hand-held communication and diagnostic device 22 must prevent injection of energy into the process control loop. To satisfy this requirement, an FF physical layer circuit (Fieldbus MAU) 28, for example, uses a shunt current regulator to sink a direct current of approximately 20 mA and modulate that current by approximately ±8 mA during message transmission.
These two protocol communication methods are basically different and mutually conflicting. For this reason, the circuit of the hand-held communication and diagnostic device 22 is constituted so as not to sink current in the HART process control loop and not inject energy into (apply a voltage to) the FF network.
Because these are different process control loops, separate connection circuits and media access circuits (HART physical layer circuit 26 and FF physical layer circuit 28) are provided in the hand-held communication and diagnostic device 22. For this reason, there is a possibility of the hand-held communication and diagnostic device 22 being connected to a network that is different from the network to which a user wishes a connection. For example, there is a possibility that the user connects the HART physical layer circuit 26 to an FF network or connects the FF network to a HART physical layer circuit 26. In order to deal with a misconnection by the user, the hand-held communication and diagnostic device 22 is constituted so that, upon the initial connection, the physical layer circuits (MAUs) remain passive and do not modulate the network media.
The measurement circuits of the hand-held communication and diagnostic device 22 are constituted by a total of four measurement signal conditioning circuits, one for the HART physical layer circuit 26 and three for the FF physical layer circuit 28. The HART measurement circuit 30 and the Fieldbus measurement circuit 32 form circuits that can sink a small-amplitude, short-duration current from the network. The Fieldbus measurement circuit 32 is constituted by three measurement conditioning circuits (collectively, the Fieldbus measurement circuit 32) that can condition the voltage signals from the FF network terminals (24b and 24c) so as to measure the DC voltage value, the amplitude value of the communication signal, and the amount of noise on the network and the loop. The HART measurement circuit 30 is formed by a circuit that measures the DC voltage value on the network. These four signal conditioning circuits are connected to the control logic block 34. The control logic block 34 includes a multiplexer connected to an A/D (analog-to-digital) converter 36. The control logic block 34 can be accessed from a microprocessor 38 via a 16-bit parallel bus 40.
When the hand-held communication and diagnostic device 22 is first turned on, the A/D converter 36 alternately monitors the DC voltages of the connection terminals of both the HART and FF networks in accordance with a command from the microprocessor 38. In this state, the hand-held communication and diagnostic device 22 will not interfere with (for example, sink or source current to and from or source voltage to) the network (process control loop).
When the hand-held communication and diagnostic device 22 is not connected to a network, the measured voltage values at both loop connection terminals are substantially zero. When one of the MAU terminals is connected to the loop via the terminals 24a and 24b or 24c and 24b, a DC voltage will be measured at that MAU terminal, and a DC voltage will not be measured at the other MAU terminal. In the HART process control loop connection, a DC voltage of approximately 12 to 50 V is measured, and in the FF loop connection, a DC voltage of approximately 9 to 32 V is measured.
With regard to the mechanical design of the loop connection terminals, the design is made so that it is not possible to connect both the HART and the FF media access units (MAU: media access units), that is, the HART physical layer circuit 26 and the FF physical layer circuit 28 to the processing loop at the same time. By doing this, even if a DC voltage is measured at one media access unit, a DC voltage is not measured at the other unit.
If a DC voltage is measured, the polarity of the DC voltage is sensed to verify whether the loop connection leads are properly connected. In particular, if the DC voltage measured between the common terminal 24b and one of the connection terminals 24a and 24c has a negative polarity, this means that the process loop connection leads are reversed. A message is sent to the host microprocessor (not shown) from the microprocessor 38, via the COM-1 terminal 41. The host processor displays the message, notifying the user to reverse the loop connection.
There is an overlap between the DC operating voltages used on both HART and FF process communication loops. Given this, the DC voltage alone cannot be used to reliably display the type of loop to which the hand-held communication and diagnostic device 22 is connected. Thus, in order to determine the type of loop, the hand-held communication and diagnostic device 22 actually measures the DC impedance of the process control loop (a considerable DC voltage value and the precise connection polarity).
The hand-held communication and diagnostic device 22 measures the DC impedance of the network by sinking a current of 1 mA for a very short duration of approximately 5 milliseconds. This interference signal generates a voltage pulse in the process control loop that is proportional to the DC impedance thereof. A clear-cut range of impedance exists between the HART and the FF process communication loops. The signal observed by the hand-held communication and diagnostic device 22 in response to the interference signal includes either the HART or the FF communication signal on the process control loop. Passing that communication signal through an appropriate low-pass filter to filter it enables observation of the short-duration pulse by the hand-held communication and diagnostic device 22.
The A/D converter 36 measures the voltage amplitude of the interference signal. The network impedance can be calculated from the measured voltage value. In the case of an FF network, the calculated value of impedance is approximately 50Ω, and in the case of a HART network the calculated value of impedance substantially exceeds 125 Ω.
In the case in which the detected loop type is different from the media access unit (MAU) connected to the hand-held communication and diagnostic device 22, an error message is sent to the host processor from the microprocessor 38, via the COM-1 terminal 41, thereby telling the user to change the network connection to the correct media access unit. If, however, the detected network, that is, the type of process control loop, is the same as the media access unit of the hand-held communication and diagnostic device 22, normal communication is continued.
Even during connection of the hand-held communication and diagnostic device 22 to the process control loop for the purpose of communication, the hand-held communication and diagnostic device 22 performs a plurality of diagnostic measurements, as necessary. For example, the microprocessor 38 periodically measures the DC loop voltage and verifies whether it remains precise and constant. If there is fluctuation in the DC loop voltage, the judgment is made that a problem has occurred in the process loop, or that the occurrence of a problem is imminent.
It is preferable that the Fieldbus measurement circuits 32 are caused to perform additional measurement diagnostics for an operating network or process control loop. The AC measurement circuit measuring the communication signal preferably is provided with a filter that enables measurement of the amplitude of message signals on the Fieldbus process control loop. Although a noise measurement circuit also can measure an AC voltage, if a low-pass filter is provided, it can measure the noise amplitude value in the range from 60 to 120 Hz.
In a hand-held communication and diagnostic device 22 having the above-noted constitution, the loop connection of a pair of loop connection terminals is automatically sensed. Additionally, the hand-held communication and diagnostic device 22 automatically senses an improper loop connection state, and can warn the user to reverse the polarity. With the hand-held communication and diagnostic device 22, the type of process control loop to which connection is made can be automatically sensed, enabling communication suitable thereto.
The hand-held communication and diagnostic device 22 can also perform a number of diagnostics of the process loop to which it is connected. Specifically, the hand-held communication and diagnostic device 22 can measure the DC network voltage, the FF message signal amplitude value, and the low-frequency noise amplitude value. Additionally, in relation to the FF diagnostics, the hand-held communication and diagnostic device 22 measures the amplitude of the Fieldbus signal strength and isolates it from a prescribed apparatus connected to the network. The user can diagnose the health of a device connected to the FF network or the loop or determine if a problem exists in a terminal of the network. Also, the hand-held communication and diagnostic device 22 can perform a plurality of FF diagnostics. The hand-held communication and diagnostic device 22 can also display information regarding a plurality of terminals provided on the FF network.
The hand-held communication and diagnostic device 22 also has a ROM 42, which is a non-volatile memory, a RAM 44, which is a volatile memory, a HART modem 45, a media access controller 46, a COM-2 terminal 47, and a debugging terminal 48 and the like. The memory within the hand-held communication and diagnostic device 22 is also used to store, along with a record of all retry queries, a full record of all detected message signal errors. These errors are associated with specific process apparatuses or receiver nodes in the process control loop. Given this, along with collection of information for the entire period of time, display is made of the status of connected nodes and the health of the loop.
In another example, the ROM 42 is a flash memory, into which are stored program commands that simplify higher-level diagnostic functionality. Such higher-level diagnostic functionality includes, for the purpose of supporting troubleshooting other apparatuses on the network, monitoring the control state of the loops operating in the FF part and/or simulating a particular functional block within the control loop.
However, in the conventional device described in Published Japanese Translation of the PCT Application 2005-522069, in addition to two different communication protocols being provided, two terminals are provided for connection to the prescribed network based on each of the communication protocols. As a result, it is necessary to take countermeasures to prevent misconnection, so that a user such as an on-site maintenance worker connects the prescribed network to the prescribed terminal.
If an incorrect connection is made between a terminal and a network, not only is a communication connection not made with the field device, but, in the worst case, the field device could be damaged.